Friction welding device

ABSTRACT

A friction-welding device for the integral joining of components, having an oscillator, which generates a periodic movement of a component and a welding surface provided thereon relative to another, static component and a welding surface provided thereon, with directions of movement parallel to the welding surfaces, having a compression device which presses the welding surfaces together, and a cartridge which accommodates the moved component. The oscillator includes two or a greater, even number of piezoactuators, which are arranged in pairs on a line of application and are able to be prestressed with respect to the cartridge from opposite sides under pressure generation and are able to be moved in a synchronous, oscillating manner together therewith and the component.

FIELD OF THE INVENTION

The present invention relates to a friction-welding device for theintegral joining of components.

BACKGROUND INFORMATION

Certain friction-welding devices are conventional. One distinguishingcriterion is the utilized kinematical principle. In the case at hand,devices are involved in which one of two components to be joined is heldstatically, the other is moved in an oscillating manner, i.e.,periodically moved back and forth, and is pressed against the staticcomponent in the process. The periodic movement occurs parallel to theprovided welding surfaces and is generated by a so-called oscillator.The pressing occurs perpendicular to the welding surfaces with the aidof a suitable compression device. Due to the high compression andfriction forces, the usually smaller, moved component is retained in asturdy cartridge that leaves only the welding zone accessible in mostcases. The oscillatory movement may be implemented on a straight and/orcurved path, for instance on a portion of a circular arc. In thestraight-line variant, the designation “linear friction welding”,abbreviated LFW, is often used. In view of the high dynamic stresses,all elements of a friction-welding device must be designed as especiallyrobust and dimensionally stable elements which are free from play, whichapplies especially when larger components made of high-strength metalsare welded. Also important are precise, reproducible and variablefriction and compression movements with high positioning accuracy at theend of the dynamic friction process. All of these criteria, after yearsof development, have had the result that mechanical and hydraulicvariants as well as combinations of the two have become accepted for thedirect generation of the required forces and motions. It is understoodthat the corresponding drives also include electromotors, electronicopen-loop and closed-loop controls, i.e., electrical and electronicelements.

European Published Patent Application No. 0 513 669 describes afriction-welding method for the blading of a blade carrier for turboengines together with the required device and device elements. Theactual implementation of this friction-welding device operates with theaid of an electromotorically driven, mechanical oscillator according toan eccentric principle, as well as with an electro-hydraulic,pressurized hydraulic compression device.

In mechanical oscillators the maximum movement frequency is limited tovalues below 100 Hertz (Hz). In hydraulic oscillators the maximumfrequency is above 100 Hz but still below 150 Hz. According to theequation power—force×velocity, the friction power is proportional to thefriction force, the movement amplitude and the movement frequency. Thefriction force results from the normal force and the coefficient offriction. At a predefined amplitude, predefined frequency (cf. abovemaximum values) and predefined coefficient of friction, the frictionpower can be increased or influenced only via the normal force/pressureforce. At a predefined friction power, the relative low frequencies ofthe mechanical and hydraulic oscillators result in correspondingly highcontact pressures that have to be generated by the compression device.High forces require mechanically especially robust and massive, i.e.,heavy, components for the friction-welding device.

SUMMARY

An example embodiment of the present invention may provide afriction-welding device for the integral joining of components havingperiodic movement of one component, which may yield geometrically moreprecise integral components as a result of more precise and betterreproducible function, and which may allow the manufacture of morefiligreed constructions due to higher movement frequencies and lowerfriction power, lighter and smaller, space-saving device elements beingutilizable in the welding area.

According to an example embodiment of the present invention, theoscillator may include two or a higher, even number of piezoactuators,which are arranged in pairs at least approximately on a line ofapplication. The piezoactuators exert compressive forces from oppositesides on the cartridge having the moved component, so that a definedprestressing is able to be realized, and the periodic friction movementoccurs practically without play. Via the electric voltagecontrol/regulation of the piezoactuators with the possibility of actingon each actuator individually, it is possible to select the mechanicalprestressing of the cartridge, the movement frequency, the movementamplitude, and the zero position of the movement, including the finalposition at the end of the welding operation, very precisely and in areproducible manner. The requirement of complicated refinishing tocompensate for geometrical inaccuracies of the welded unit, for instanceby NC milling, may thereby be considerably reduced or eliminated. Due tothe lower frictional forces, a smaller and lighter cartridge etc., it isalso possible to use friction welding to produce and repair filigreed,mechanically sensitive blisks (bladed disks) with narrowly positionedblades. In the process, the hubs/disks of the rotors may be able to beoptimally adapted to the operating loads and for the most part be fullyfinished, so that they may no longer have to be provided in oversize orwith considerable allowances in view of the friction-welding loads, suchallowances having to be removed again later on.

Example embodiments of the present invention are explained in greaterdetail below with reference to the appended Figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the axial detail of a blade carrier having a blade tobe affixed thereon.

FIG. 2 illustrates the detail illustrated in FIG. 1, supplemented by afriction-welding device.

FIG. 3 illustrates the radial detail of the blade carrier, the blade andthe friction-welding device illustrated in FIG. 2.

FIG. 4 illustrates the tangential detail of a blade carrier, a blade anda friction-welding device having four pairs of actuators.

FIG. 5 illustrates the detail of a piezoactuator having a flat springarrangement.

FIG. 6 illustrates an arrangement of piezo elements.

DETAILED DESCRIPTION

FIG. 1, in an axial view, illustrates a portion of a blade carrier 4intended for a rotor of a turbo engine on which a blade 3 is to beaffixed by friction welding. The oscillating friction movement is tooccur transversely to the longitudinal center axis of blade carrier 4,which is indicated by a horizontal double arrow for friction force Fr.Only blade 3 is moved in the process. Blade carrier 4 is heldstatically. Welding surfaces 5, 6 are pressed against each other by acompression force Fs directed perpendicular to the surfaces, compressionforce Fs being introduced into welding zone 7 via moved blade 3. Theforce arrow pointing toward the blade tip from above is irrelevant forthe actual type of force application into blade 3. To be preferred, forexample, is a force application producing an even loading, if possible,of a large portion of the blade surface by a frictionally engaged or akeyed connection.

In addition to components 3, 4 to be friction-welded, FIG. 2 illustratesa friction-welding device 1 according to an example embodiment of thepresent invention. For better understanding, FIG. 3 should be referredto as well. To transmit the considerable forces, blade 3 is virtuallycompletely encased in a mechanically sturdy cartridge 11, e.g., made ofsteel or hard metal, the inner contour of cartridge 11 being adapted tothe blade contour in a best-possible manner. Cartridge 11 includes twoor more parts which are screwed together and have separating lines thatare adapted to the blade geometry. In addition to cartridge 11,oscillator 8, which generates a defined, periodic friction movementparallel to welding surfaces 5, 6, and compression device 10, whichproduces a defined compression force and feed movement, are componentsof friction-welding device 1. In the present example embodiment, bothoscillator 8 and compression device 10 operate according to thepiezoelectrical principle, i.e., on the basis of linear deformation ofthe piezoelements caused by electric direct voltage. Illustrated in FIG.1 are two horizontal piezoactuators 12, 13 of oscillator 8, which are ona line of application and engage with cartridge 11 from the left andright, as well as a piezoactuator 16 of compression device 10, whichengages with cartridge 11 vertically from above. The force-transmissionpoints between the piezoactuators and cartridge 11 may have one or moredegrees of freedom, depending on the relative movement, for instance fortranslatory displacements and/or swiveling motions. Slide bearingsand/or roller bearings may be used in this context. In the case at hand,for instance, a pivoting joint with a degree of freedom may be arrangedbetween piezoactuator 16 and cartridge 11. The implementation of theforce-transmission points may be conventional. The drawn-in doublearrows indicate a synchronous, equidirectional motion of piezoactuators12 and 13.

Aspects hereof become even more apparent with reference to FIG. 3. Thisradial detail of blade carrier 4 and blade 3 indicates the blade profileencased by cartridge 11 and the separating lines of cartridge 11 adaptedthereto. Longitudinal center axis X of the blade carrier, i.e., itslater axis of rotation, extends vertically in this view. It should beunderstood that, in a new blading of blade carrier 4, a multitude ofblades 3 positioned in close proximity to one another must be affixed atthe circumference, only one of which is illustrated for clarity. As aresult, cartridge 11 may have to be arranged such that there is room forit between already installed blades. This is the explanation for theoffset form of the cartridge illustrated. In the case at hand,oscillator 8 has four piezoactuators 12 to 15, which are arranged inpairs on a line of application and are situated transversely tolongitudinal center axis X. It should be noted that the piezoactuatorsmay have lengths of several meters due to the required oscillationamplitudes of several millimeters, a multitude of piezoelements beinggeometrically connected in series, i.e., are arranged one after theother. Therefore, it is possible to arrange the long piezoactuators 12to 15 in the manner illustrated, in pairs, axially in front and behindthe bladed, or to be bladed, blade carrier 4. It should be noted thatfriction-welding device 1 may be used both for the production of newparts and for repair purposes (repair), i.e., for the replacement ofindividual or several blades. The two front piezoactuators 12, 13 aresynchronously controlled such that they may always rest againstcartridge 11 under compressive stress. The same applies to the two rearpiezoactuators 14 and 15. Also, it may be likely that the front actuatorpair is operated at the same frequency as the rear actuator pair. Givenan in-phase condition and identical amplitude of the front and rearactuator pair, blade 3 executes a straight oscillating motion. However,there are also the options of operating an actuator pair at differentamplitude and/or with a phase shift relative to the other, yet at thesame frequency. For blade 3 that means that combinations of translatorymotions and swiveling motions or pure swiveling motions about variablepivotal points are possible. In this context, reference is made to thestraight and the curved double arrow above blade 3. This may require acorrespondingly flexible connection of piezoactuators 12 to 15 tocartridge 11. Using locally different forms of movement and differentamplitudes, the introduced friction energy may be varied across thewelding surfaces, for instance, less friction energy in thin bladeregions than in thick regions, so that an even temperature distributionand, ultimately, a better welding result may be achieved.

FIG. 4 illustrates a detail of blade carrier 4 with blade 3 in thecircumferential direction/tangential direction, longitudinal center axisX of blade carrier 4 extending vertically and to the right next to theactual representation. Friction-welding device 2 utilized here differsfrom the above-described friction-welding device 1 in that itsoscillator 9 includes four pairs of piezoactuators, i.e., eightpiezoactuators, the representation showing only the four piezoactuators17 to 20, which are arranged in front of cartridge 11 in the view.Relative to longitudinal center axis X, the effective plane ofpiezoactuators 17, 18 is at a greater radial height H2 than theeffective plane of piezoactuators 19, 20, which is at radial height H1.Blades may exhibit a slight, undesired tilt in the circumferentialdirection after welding despite precise radial alignment in thecartridge. Utilizing the illustrated, height-offset actuator pairs maymake it possible to adjust a selective small, oppositely-directed tiltof cartridge 11 and blade 3 in the circumferential direction during thewelding operation, for instance by geometric shifting of the zero pointof the higher actuator pairs relative to the lower actuator pairs, sothat the exact desired blade orientation results at the end of thewelding operation. Compression device 10 having piezoactuator 16 mayhave the same arrangement as in the previous figures.

The movement amplitudes of piezoactuators relative to the actuatorlength are in the per mill range. To reduce the actuator lengths atpredefined amplitudes, the actuator amplitudes may be mechanicallyincreased, different gear mechanisms being possible. To this end, FIG. 5illustrates a flat-spring arrangement 22 as an example. Two or more flatsprings are fixedly clamped into a static base 25 at one end. The otherends of the flat springs are embedded in a displaceable part 24. Apull/pressure element connected to a piezoactuator 21 engages with theflat springs in the region between base 25 and part 24. By elasticdeformation of the flat springs, part 24 is moved at a greater amplitudeand the same frequency in relation to the pull/pressure element. Bymoving the pull/pressure element to base 25, it may be possible toincrease the movement amplitude of part 24 while reducing the forceexerted by part 24. The movement of part 24 may not be exactly linearsince a certain swiveling motion is superposed. The kinematics closelyresemble a guidance in the form of a parallelogram.

As already mentioned, piezoactuators having amplitudes in the millimeterrange have a multitude of piezoelements in a geometrical seriesconnection. It is possible that several hundred such piezoelements maybe present. Since conventional piezoelements may be restricted incross-section, for instance to the size of a coin, for the generation ofgreat forces it may be required that a plurality of “columns” ofpiezoelements connected in series may need to be arranged in paralleland be combined in a, for instance, tubular actuator. FIG. 6, in highlysimplified form, illustrates two “columns” arranged in parallel on astatical base 26. The two columns lead to a displaceable yoke 27 whichhas the same movement amplitude as each of the columns, at twice thecompressive force compared to a single column. More than two collimated“columns” may be combined in one actuator. The geometrical/constructiveserial or parallel connection should not be confused with the electricalcircuit of the piezoelements where electrical serial and parallelconnections are used as well, the latter especially for the purpose oflimiting voltages.

1-9. (canceled)
 10. A friction-welding device for integrally joiningcomponents, each component including a welding surface, comprising: anoscillator adapted to generate a defined periodic movement of one of thecomponents and the welding surface of the one of the components relativeto another one of the components that is held statically during weldingand to the welding surface of the another one of the components, theperiod movement including directions of movement parallel to the weldingsurfaces; a compression device adapted to press the welding surfaces ofthe one of the components and the another one of the components againsteach other at a defined force; and a cartridge adapted to accommodatethe one of the components outside of a welding zone; wherein theoscillator includes an even number of piezoactuators arranged in pairsat least approximately on a line of application, the piezoactuatorsprestressable with respect to the cartridge under pressure generationfrom opposite sides by piezoelectric liner deformation, thepiezoactuators displaceable with the cartridge and the one of thecomponents synchronously oscillatingly at cartridge-side ends.
 11. Thefriction-welding device according to claim 10, wherein the componentsinclude hydraulically effective blades having one of (a) disk- and (b)ring-shaped blade carriers.
 12. The friction-welding device according toclaim 10, wherein the friction-welding device is adapted to produce andrepair integrally bladed rotor components of turbo machines.
 13. Thefriction-welding device according to claim 10, wherein the compressiondevice includes at least one piezoactuator having a piezoelectricallymovable end couplable to the cartridge to introduce a definedcompression force perpendicular to the welding surfaces.
 14. Thefriction-welding device according to claim 10, further comprising adevice adapted to enlarge relatively small, linear motions of thepiezoactuators to generate greater movements having at least one of (a)straight and (b) curved paths.
 15. The friction-welding device accordingto claim 10, wherein the device includes at least one of (a) amechanical gear, (b) a lever mechanism, (c) a flat spring arrangement,(d) a cam gear and (e) a crank control.
 16. The friction-welding deviceaccording to claim 10, wherein the friction-welding device is adapted tojoin blades to one of (a) a disk- and (b) a ring-shaped blade carrier,lines of application of the piezoactuators extending transversely to alongitudinal center axis of the blade carrier, a first pair ofpiezoactuators engaging with a front end of the cartridge from oppositesides on a line of application axially in front of the blade, a secondpair of piezoactuators engaging with a rear end of the cartridge fromopposite sides on a line of application axially behind the blade. 17.The friction-welding device according to claim 10, wherein thefriction-welding device is adapted to join blades to one of (a) a disk-and (b) a ring-shaped blade carrier, lines of application of thepiezoactuators extending transversely to a longitudinal center axis ofthe blade carrier, two first pairs of piezoactuators, each arranged on aline of application, engaging with a front end of the cartridge fromopposite sides, axially in front of the blade at different radialheights relative to the longitudinal center axis of the blade carrier,two second pairs of piezoactuators, each arranged on a line ofapplication, engaging with a rear end of the cartridge from oppositesides, axially behind the blade, at different radial heights relative tothe longitudinal center axis of the blade carrier.
 18. Thefriction-welding device according to claim 16, wherein at least one pairof piezoactuators engaging with the axially front end of the cartridgeare moveable in relation to at least one pair of piezoactuators engagingwith the axially rear end of the cartridge, are movable at a samefrequency, with one of (a) a same and (b) a different amplitude and inone of (a) an in-phase and (b) a phase-shifted manner.
 19. Thefriction-welding device according to claim 17, wherein geometrical zeropoints of the oscillation movements of the first pairs of piezoactuatorsare displaceable relative to one another, geometrical zero points of theoscillation movements of the second pairs of piezoactuators displaceablerelative to one another.
 20. The friction-welding device according toclaim 10, wherein a force/path characteristic of the piezoactuators isselected by geometrical serial and parallel connection of piezoelements.21. The friction-welding device according to claim 10, wherein a maximumrequired electrical voltage of the piezoactuators is limited byelectrical serial and parallel connection of piezoelements.